Although a relatively obscure metal, thallium is found in many mining waters and because of its toxic nature, must be removed to low levels. A low-cost natural zeolite, clinoptilolite, has been found to effectively remove thallium from water at a closed gold mine. Zeolites have a high affinity for thallium but also remove other cationic metals from solution.
This system treats up to 80 gpm of mine water. Anticipated costs for clinoptilolite, which can be disposed of as a nonhazardous waste, are only about $8,000/year.
The Kendall process plant at this closed gold mine near Lewistown, Montana
The five gravity-flow columns filled with natural zeolites to remove thallium from mine water
Natural zeolites evaluated in bench-scale, pilot-scale and full-scale tests
Here's a paper on the project: